1. Field of the Invention
The field of this invention is nucleic acid hybridization.
2. Background of the Invention
The detection of nucleic acid hybridization events is a fundamental measurement in a variety of different life science research, diagnostic, forensic and related applications. A common feature of nucleic acid hybridization assays is that target and probe nucleic acids are combined under hybridization conditions and any hybridization events occurring between complementary target and probe nucleic acids are detected. The detection of hybridization events, i.e. target/probe duplexes, is then used to derive information about the source of the target nucleic acids, e.g. the genes expressed in a cell or tissue type, and the like.
In currently employed hybridization assays, the target nucleic acid must be labeled with a detectable label (where the label may be either directly or indirectly detectable), such that the presence of probe/target duplexes can be detected following hybridization. Currently employed labels include isotopic and fluorescent labels, where fluorescent labels are gaining in popularity as the label of choice, particularly for array based hybridization assays.
While fluorescent labels provide a number of advantages over other types of labels in hybridization assays, they are not ideal. For example, it is difficult to obtain quantitative results with fluorescent labels. Furthermore, fluorescent label based assays can be relatively slow and are difficult to scale up.
Accordingly, there is continued interest in the development of new hybridization assay protocols. Of particular interest would be the development of a hybridization assay protocol in which the presence of hybridized target and probe could be detected without the use of labels, such as fluorescent labels.
Bean et al., J. Appl. Phys. (1970) 41:1454-1459; DeBlois et al., J. Coll. Interface (1977) 61:323-335; and Kasianowicz et al., Proc. Nat""l Acad. Sci. USA (1996) 93:13770-13773.
Methods are provided for determining the presence of double stranded nucleic acids in a sample. In the subject methods, nucleic acids present in a fluid sample are translocated through a nanopore, e.g. by application of an electric field to the fluid sample. The current amplitude through the nanopore is monitored during the translocation process and changes in the amplitude are related to the passage of single- or double-stranded molecules through the nanopore. The subject methods find use in a variety of applications in which detection of the presence of double-stranded nucleic acids in a sample is desired, e.g. in hybridization assays, such as Northern blot assays, Southern blot assays, array based hybridization assays, etc.